NEW YORK (CNN/Money) - Charter Communications Inc. said Friday a grand jury subpoenaed documents related to the company's customers and bookkeeping, making Charter the second U.S. cable company to have its accounting called into question, after Adelphia Communications.

Charter, the fourth-largest U.S. cable provider, said the U.S. Attorney's office for the Eastern District of Missouri issued the grand jury subpoena related to current and disconnected customers and policies and procedures related to the way it capitalized or expensed certain costs.

Jim Martin, a spokesman for the U.S. Attorney, confirmed the subpoena but declined to comment on the nature of the situation.

On Feb. 11, Charter disclosed that it increased reserves for uncollected accounts as of Dec. 31, and that it had tightened its collection policy and procedures related to marginal customers. Charter also said it expected to remove about 120,000 marginal customers from its basic account in the first quarter of 2002.

The company disclosed in its quarterly financial report for the period ended March 31 that it had increased that amount to 145,000 customers.

"Charter believes the issues under investigation are similar to those raised in previously reported class actions pending against the company, and certain individual defendants, and will cooperate fully with the subpoena," Charter spokesman David Andersen said in a statement. The company could not be reached for further comment Friday.

Shares of Charter (CHTR: down $0.09 to $2.62, Research, Estimates) were down slightly to $2.53 Thursday, well off their 52-week high of $21.20.

Charter's woes come on the heels of accounting problems at Adelphia Communications. The sixth-largest cable provider disclosed earlier this year that it had billions of dollars of off-balance-sheet loans guaranteed by the company to its founders, the Rigas family, inflated profits and other irregularities.

Three members of the Rigas family, all of whom resigned earlier this year, were arrested last month for securities fraud, accused of looting the company and using its coffers as their "personal piggy bank."